The objective of the proposed study is to develop and evaluate a combined flow cytometric/cell sorting/autoradiographic technique to monitor acute leukemias of adults and children. The data obtained, to be determined serially through stages of disease, will provide a more precise means of predicting relapse and of evaluating treatment protocols. Aneuploidy, present in more than 50 percent of the childhood and in 16 precent of the adult leukemias, will serve as a marker. Flow cytometric DNA-RNA measurements, also useful in the classification of leukemias, will determine the leukemic DNA stemline, and thus detect aneuploidy. Patients with aneuploidies will be followed serially during induction, consolidation and maintenance therapy and thereafter. Identification of aneuploid leukemic cells will be performed in three different ways: 1) for high levels of leukemic cells (more than 5 percent) multiparameter DNA/RNA flow cytometry measurements of more than 1 million mononuclear cells per sample (blood and bone marrow); 2) for low levels of leukemic cells (1-5 percent) enrichment of leukemic cell populations by velocity sedimentation and flow cytometry; and 3) for very low levels less than 1 percent combined flow-cytometric cell sorting/autoradiographic techniques. This last procedure will distinguish very low numbers of hyperdiploid leukemic G1 cells from normal DNA synthesizing cells. In addition, we will try to identify euploid as well as aneuploid leukemic cells by differences in chromatin structure, as determined by flow cytometric measurements of acridine orange binding after acid and thermal denaturation. These results will permit monitoring the effects of therapy by quantitating very low levels of leukemic cells in blood and bone marrow (less than 0.1 percent), serially during "complete remission" and in early relapse. This represents a 50-fold increase in sensitivity over present methods and can be expected to assist in therapeutic decisions and in design and modification of treatment protocols.